Maybe try the clip lit. You can clip it to the back of the harness, so you can see it from behind. It is not as heavy as the night ize tag, but you do have to replace the battery occasionally.
It wouldn't work on a collar probably, since it might make it slide around to the front. If it is for walks at night it would be great, but in the back yard maybe not.
I will order it and try it for my puppy, I'll report back
Thanks for the tip on the rechargeable collar. Is that the one that is supposed to fit all?